This invention relates to generating maintenance recommendation messages in response to the rate of occurrence of notable events or conditions exceeding variable thresholds which are continuously adjusted in dependence upon said rate of occurrence.
Elevator maintenance is currently scheduled in response to the amount of time which has elapsed since the previous maintenance, or in response to the number of operations of an elevator, subsystem or component since the previous maintenance. This results in performing unnecessary maintenance on some equipment, and performing less than adequate maintenance on other equipment.
A recent innovation is disclosed in commonly owned copending U.S. patent applications Ser. No. 09/898,853, filed Jul. 3, 2001, now U.S. Pat. No. 6.516.923, and Ser. No. 09/899,007, filed on Jul. 3, 2001. In said prior pair of applications, a large number of elevator door events and conditions are monitored, and maintenance messages are provided to assist service personnel in response to occurrence of certain notable events. In the systems disclosed in said applications, in some instances, the occurrence of a notable event only a single time (such as an average value being too high) will cause maintenance messages to be generated; in other cases (such as a door opened or closed position being wrong), the maintenance message will be generated only after a threshold number of occurrences of that notable event, but that threshold number is fixed. While those systems provide condition-related maintenance messages, rather than being based upon elapsed time or number of operations alone, the need for service is still not tailored to the particular elevator. As an example, it may happen that in one elevator, that certain notable events or conditions may occur rather frequently, even though there is nothing wrong with any components of the elevator, and there is no service which, when performed, will alter the situation; but it may happen in another elevator that the same notable events or conditions occurring the same or fewer number of times may be indicative of a faulty component for which service is required: the foregoing systems do not separate therebetween.
Objects of the invention include: reducing unnecessary elevator maintenance; improving elevator maintenance to the level which is required; providing the proper level of maintenance to elevators; elevator maintenance which can take into account the variation in condition of parameters between elevators, which are altered by deviations in the environment and by deviation in the maintenance provided thereto; provision of maintenance recommendations which permit service personnel to concentrate on elevator conditions that are likely to disrupt normal elevator operations; improved elevator service quality; and reduced elevator service cost.
This invention is predicated on the perception that the occurrence of notable events or notable values of parameters, herein referred to as xe2x80x9cdefectsxe2x80x9d, may or may not be indicative of the need to replace or to provide service to a component or subsystem of the elevator. This invention is further predicated on the discernment of the fact that deterioration of elevator components, subsystems, or adjustments are best indicated by the trends in notable elevator events or conditions.
According to the present invention, the occurrence of events or conditions which are deemed notable with respect to the need for elevator maintenance, herein referred to as xe2x80x9cdefectsxe2x80x9d, are utilized to generate operation-averaged rate of occurrence of such defects, which in turn are utilized to generate thresholds for each such defect, the thresholds in turn being utilized to signal the need for maintenance recommendation messages. According to the invention, for each possible defect being monitored, there is a finite but variable algorithm period, which may for instance be on the order of when several defects have occurred, when the number of operations exceed 2,000 operations, or after the elapse of 14 days. At the end of each algorithm period, the rate of defects (number of defects ratioed to the total number of operations of the related element or subsystem) is calculated; then a new threshold deviation is calculated based upon the established average defect rate and the number of operations during the algorithm period; then upper and lower thresholds are calculated based on the recently calculated threshold deviation and the established average defect rate.
An internal flag is generated if the new defect rate exceeds a maximum upper threshold, or if the new defect rate and the next prior defect rate exceed their respective upper thresholds. The average defect rate is updated if three rates in a row either exceed or are less than corresponding thresholds; upward adjustments of the average defect rate being limited by number of operations and time since a maintenance flag was generated during a visit of service personnel.
The invention comes into play when there is either a request for information (such as from a central elevator monitoring facility) or a visit by service personnel. In either such case, a maintenance recommendation message will be indicated for any parameter for which there was an upward adjustment of the average rate of defects without a subsequent downward adjustment thereof, or if an internal flag had been generated for that parameter since the last visit of service personnel, and no downward adjustment of the average defect rate had occurred since then.
The particular maintenance recommendation message depends on the parameter which causes it, and other related factors, examples of said messages being set forth in the prior pair of applications.
The maintenance recommendation messages of the invention may be indicated only when requested by either a remote maintenance facility issuing a request for information, or by service personnel indicating that a maintenance visit is ongoing. On the other hand, the invention may be used to generate alerts and alarms in a fashion similar to that known to the prior art, or used otherwise.
The conditions under which maintenance recommendation messages are given differ significantly from the prior art. First, these messages are condition-dependent, being dependent upon the actual parameters of the elevator indicating notable events or conditions, called defects herein. Furthermore, not every notable event or condition is acted upon, the ones which are generated in accordance with the present invention are acted upon only when the rate of occurrence of defects exceeds variable, automatically updated thresholds for that particular parameter in that particular elevator, based upon recent operation of that elevator. Thus, only circumstances indicative of a degradation of elevator performance will result in maintenance recommendation messages being indicated, thereby limiting maintenance to that which is truly necessary in that particular elevator at that particular time.
Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.